The NFL deliberately stays away from using every resource because holding would be called on every play, because Wilfork was held on his facemask, because Banta-Cain had his facemask grabbed on his penalty.
Let me rewind this and see what you think.
It's the end of the game and Merriweather makes the game-ending interception. The Pats offense comes onto the field. While the refs are standing around, they see a replay of the pass rush that lead to the bad throw from Flynn. They see Tully's hands to the face of the O-lineman.
They decide to throw a flag.
The Patriots offense must leave the field and the game is no longer over.
Can you honestly imagine that scenario?